A barcode is an existing machine-readable representation of data using lines or bars of varying thicknesses parallelly spaced relative one another in a specified area. This type of barcode is referred to as a one-dimensional barcode (1D-barcode), and are commonly seen printed on or associated with products, publications, displays, labels, and documents. Uniform Product Code (UPC) and UPC-A and UPC-E variants thereof, EAN-8, EAN-13, ITF-14, Code128, Code39 are some examples of 1D-barcodes used in the retail industry.
Several forms of two-dimensional barcodes, or two-dimensional codes (2D codes) are also presently available. Quick Response code (QR code) is a well-known example of 2D-codes (QR code is a registered trademark of Denso Wave Incorporated, in the United States and in other countries). PDF417, DataMatrix, MaxiCode, GridMax, Aztec code, and ShotCode are some examples of 2D-barcodes used in a variety of industries (any code named herein, which is also a trademark, is owned by its respective owner).
A 1D-barcode carries a small amount of information, usually just enough to represent ten or twenty alphanumeric characters as an example. A 2D-code on the other hand can be configured to carry different amounts of data. Extreme cases of 2D-codes have been configured to carry even several kilobytes of data.